1. Field of the Invention
This invention relates to a structure of conductor to be used in a thin film integrated circuit and hybrid integrated circuit, and a method for preparing the same.
2. Description of the Prior Art
In integrated circuits, wirings are often cross-connected to other conductors on account of arrangements of parts. In the conventional thin film integrated circuits, cross-over parts of conductors are coated with an insulating material at first, and then the conductors are crossed, but an adhesive strength between the insulating material and the conductors is low. As a result, peeling of the insulating film or conductors film occurs.
To improve these drawbacks, there has been proposed a structure prepared by using an anodizable metal as a conductor and anodization at the surface of the metal, thereby forming an insulating film. There has been also proposed another structure of multi-layer conductor prepared by forming an anodizable metal on a substrate, then coating the metal with a photoresist in a desired conductor shape, anodizing the entire thickness of the metal, thereby obtaining flat surface circuits insulated with anodized film, then forming an insulating film of silicon oxide, etc., on the surface of the conductor, partially removing cross parts of the conductor by etching, forming again a second metal capable of forming an anodized film, and anodizing the second metal, thereby forming an anodized film throughout the entire thickness of the conductor and crossing the conductors. However, even in the latter conventional art, the adhesive strength is not so high, because there is a silicon oxide film between the conductors, and as a result, peeling is liable to take place. There have been also proposed methods for replacing the silicon oxide film with an anodized film in said structure or for anodization at the surface of the conductor, but it is not possible to form windows on the anodized film, because there is not available an appropriate etching solution for the anodized film, or even when partial etching is attempted, using a photoresist, it takes a long time in the etching of the anodized film, and the photoresist is deteriorated during the etching, losing the function as the photoresist. Furthermore, when it is tried to form anodized films partially, by using a chromic acid solution and masking by using a photoresist, chromic acid solution is permeated under the photoresist owing to the deterioration of the photoresist, and the anodized films are not formed in an exact shape. Furthermore, the anodized film formed by the chromic acid solution permeated under the photoresist is not readily etched for the same reason as above.
As a result of various studies on selective etching of the anodized film, particularly, that of aluminum, the present inventors have found that chemical resistances of anodized films depend upon kinds of anodization methods, and thus selective etching is possible to carry out. As a result, a conductor structure, whose cross-connectional parts are electrically connected, can be provided in the present invention.